In recent years, as a long-distance transmission network, introduction of the OTN (Optical Transport Network) has been progressed. In a signal transmission frame defined in the OTN (hereinafter referred to as an “OTN frame”), a variety of client signals can be mapped to the same frame. Examples of the client signals may include signals of SONET (Synchronous Optical Network), SDH (Synchronous Digital Hierarchy), Ether Network (Ethernet®), and fiber channels.
Accordingly, as illustrated in FIG. 13, a recent transport (or transmission) apparatus 300 is placed between SONET/SDH network 400, Ethernet 500 and OTN 600. In the transport apparatus 300, it is expected that different types of client signals are accommodated in an OTN frame. In FIG. 13, reference numeral 401 denotes a SONET/SDH termination unit used for the SONET/SDH network 400. Reference numeral 501 denotes an Ethernet termination unit used for the Ethernet 500. FIG. 13 also illustrates a SONET network 400 and a SONET termination unit.
Provisioning of multi-port and multi-protocol is being progressed rapidly in the transport apparatus 300. Accordingly, important signal chips are mounted on a circuit board used for the transporting apparatus 300, thereby increasing the amount of information for monitoring and control these chips. The multi-port is a provision to connect one transport apparatus to many other apparatuses.
As illustrated in FIG. 13, there is also a need to exchange an Ethernet monitoring control signal (frame) (hereinafter also referred to as a “monitoring control frame”) between the transport apparatus 300 and the Ethernet termination unit 501. Examples of the monitoring control frame may include an OAM (Operation Administration and Maintenance) frame, a SSM (Source-Specific Multicast) frame, and a Management VLAN (Virtual Local Area Network) frame. These monitoring frames are inserted in a predetermined position of a main signal frame. Therefore, the board of the transport apparatus 300 requires processing of monitoring control signals between apparatuses as well as monitoring control of the board and the amount of monitoring control information to be processed tends to significantly increase with the multi-port provisioning of the board.
Japanese Laid-open Patent Publication No. 07-93236 discloses a technique for connecting system console interface controllers (SCIs) in the form of a ring, requesting bus use in two ways, and performing an access process in a transmission direction in which the bus use is allowed. Japanese Laid-open Patent Publication No. 08-44660 discloses a serial bus system in which a sensor unit and a driver unit connected in series are connected to a controller in the form of a loop.